A. Field of the Invention
The present invention relates to the field of the modification of synthetic fibers used in the production of yarns used for the production of fabrics, textiles, rugs and other consumer items. More specifically, the present invention relates to the enzymatic modification of the characteristics of a polyester fiber so that such polyesters are more susceptible to post-modification treatments.
B. State of the Art
Polyesters are manufactured synthetic compositions comprising any long chain synthetic polymer composed of at least 85% by weight of an ester of a substituted aromatic carboxylic acid, including but not restricted to substituted terephthalic units and parasubstituted hydroxybenzoate units. The polyester may take the form of a fiber, yarn, fabric, film, resin or powder. Many chemical derivatives have been developed, for example, polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT) and polyethtlene naphthalate (PEN). However, PET is the most common linear polymer produced and accounts for a majority of the polyester applied in industry today.
Thermoplastic polyester can be selectively engineered in any of the basic processing steps of polymerization and fiber formation. This flexibility and range of properties allows for a wide range of products to be made from polyester for markets such as the apparel, home furnishing, upholstery, film, rigid and flexible container, non-woven fabric, tire and carpet industries. As a result, polyester has become the dominant reinforcement fiber in the United States. Moreover, while over the past 30 years cotton has continued slow, steady growth of volume consumed and wool has been virtually flat, polyester has begun to take on increased significance. Moreover, polyester has reached a high level of consumer acceptance due to its strength and the increasing quality and variety of fabrics that can be made using such fibers. Other polyester markets such as fiber-fill and non-woven articles continue to grow.
In the textile industry, polyester has certain key advantages including high strength, soft hand, stretch resistance, stain resistance, machine washability, wrinkle resistance and abrasion resistance. However, polyester is not so optimal in terms of its hydrophobicity, pilling, static, dyeability, inactive surface as a medium for adhering, i.e., softening or wettability enhancing compounds, and lack of breathability. Moreover, in the 1960's and 1970's, polyester textiles suffered from poor consumer perception and was synonymous with the phrase "cheaply made" and derided for the horrendous colors with which polyester was associated. This latter problem is due in large part to the unavailability of a large selection of dyes which are compatible with polyester. To combat this perception, the industry has made strong efforts to improve the characteristics of polyester.
One of the problem areas that the industry has sought to improve involves the characteristic that polyester is very resistant to uptake of polar or charged compositions, i.e., fabric softeners, finishes and dyes. In the past, many synthetic fibers such as those of cellulose acetate, cellulose triacetate, acrylonitrile, polyesters, polyamides and polyhydrocarbon polymers were thought not to be satisfactorily dyed with basic dyes nor with cotton dyes. Current methods for dyeing polyester include replacing chemical substitution of terephthalate with compounds such as isophthalate and sulfo-isophthalate which improve the uptake of the dye, improving chemical penetration of the dyes by using high temperature, emulsified aromatic and/or chlorinated aromatic solvents, adding colorant to the molten polyester, and the use of cross-linking polymers to glue the pigment to the fabric. U.S. Pat. No. 3,381,058 discloses a method of making a poly(1,4-cyclohexylenedimethylene terephthalate) fiber having non-fiber forming polyester dispersed therein for the purpose of improving dyeability. Similar objects are achieved by methods described in U.S. Pat. No. 3,057,827 (preparing a high molecular weight linear condensation copolyester from linear polyester forming compounds with an essential component of a sulfinite radical) and U.S. Pat. No. 3,018,272 (preparing compounds comprising a polyester using a metallic salt of a sulfonate).
Another problem with polyester relates to the difficulty of removing oily and/or hydrophobic stains. These stains often adhere strongly to the fabric or fiber and cause a permanent stain.
Thus, methods for improving the surface characteristics of polyester have been developed in an attempt to improve the dyeing, stain resistance and other properties associated with the strongly hydrophobic nature of the polyester. For example, chemical methods such as nucleophilic substitution via nucleophile attack at the ester carbonyl or hydrolysis; surface polymerization by crosslinking a topical finish to either the fiber or the fabric; chemical penetration of the polyester polymer with aromatic compounds; and topical application of a surface coating from an aqueous solution which has affinity for the polyester. Nonetheless, these processes often have inherent deficiencies such as cost of chemicals, energy and capital equipment, the use of environmentally unsafe solvents, limited flexibility and negative effects on strength of the material and other aesthetic properties of the fabrics.
GB 2296011 A discloses enzymes naturally produced by a fungus of the species Fusarium solanii var. minus T.92.637/1, including a cutinase of isoelectric point 7.2 and mol. wt. 22 kDa. which are useful in detergent compositions for removing fatty acid-based dirt and stains.
U.S. Pat. No. 5,512,203 discloses cleaning compositions comprising a cutinase enzyme and a polyesterase compatible surfactant. The microbial cutinase is from Pseudomonas mendocina and is used in an improved method for enzymatically cleaning a material having a cutin or cutin-like stain.
PCT Publication No. WO 97/43014 (Bayer AG) describes the enzymatic degradation of polyesteramide by treatment with an aqueous solution comprising an esterase, lipase or protease.
JP 5344897 A (Amano Pharmaceutical KK) describes a commercial lipase composition which is dissolved in solution with an aliphatic polyester with the result that the fiber texture is improved without losing strength. Polymers of aliphatic polyethylene are also disclosed which can be degraded by lipase from Pseudomonas spp.
PCT Publication No. 97/33001 (Genencor International, Inc.) discloses a method for improving the wettability and absorbance of a polyester fabric by treating with a lipase.
PCT Publication No. WO 99/01604 (Novo Nordisk) describes a method for depilling a polyester fiber or fabric and for color clarification of such fabrics by reacting with an enzyme which has either ethyleneglycol dibenzyl ester (BEB) and/or terephthalic acid diethyl ester (ETE) hydrolytic activity.
While advances have been achieved in the field of improving the quality of polyester, the industry remains in need of additional methods of producing polyesters with improved characteristics.